1,320 research outputs found

    Power simulator upgrade for smart grid algorithm development and testing

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    This thesis describes the conversion of WVU\u27s analog power simulator into a micro-grid of the future test bed by installing digital relays and intelligent electronic switches. The simulator is a hardware representation of the grid which contains traditional hardware, both digital and analog as well as the recent addition of highly connected, via Ethernet and potentially wireless communication, smart switching and monitoring devices. These new devices were chosen specifically for their cyber security capability to explore that facet of smart grid development. It is important to note that this simulator is a hardware implementation and as such is capable of testing smart grid ideas in the most realistic setting available without affecting real customers. This simulator also has the potential to have renewable resources like wind and solar as well as fuel cell and battery storage distributed resources tied in to test smart grid adaptability to these next generation ideas.;New digital relays were installed. Micro controller units and energy meter integrated circuits were investigated based on the desire to provide many modes of communication and as much processing power as was available in a small package. Solid state switches were designed and implemented for speed, compactness and reduced power consumption

    Optically-switched submillimeter-wave oscillator and radiator having a switch-to-switch propagation delay

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    A submillimeter wave-generating integrated circuit includes an array of N photoconductive switches biased across a common voltage source and an optical path difference from a common optical pulse of repetition rate f sub 0 providing a different optical delay to each of the switches. In one embodiment, each incoming pulse is applied to successive ones of the N switches with successive delays. The N switches are spaced apart with a suitable switch-to-switch spacing so as to generate at the output load or antenna radiation of a submillimeter wave frequency f on the order of N f sub 0. Preferably, the optical pulse has a repetition rate of at least 10 GHz and N is of the order of 100, so that the circuit generates radiation of frequency of the order of or greater than 1 Terahertz

    The AEPEX CubeSat Mission: Quantifying Energetic Particle Precipitation through Bremsstrahlung X-Ray Imaging

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    Fundamental gaps exist in the understanding and observation of energetic particle precipitation (EPP),a solar-terrestrial coupling mechanism that is vital for climatelogical modeling of the atmosphere and magnetosphere. The Atmospheric Effects of Precipitation through Energetic X-rays (AEPEX) mission is a 6U CubeSat that will measure energetic electron spectra and X-ray images in order to quantify the spatial scales and amount of energy input into the atmosphere, and therefore lost from the magnetosphere, via EPP. AEPEX includes two instruments; AEPEX’s FIRE (Focused Investigations of Relativistic Electron) instrument (AFIRE), a TRL 9 electron detector previously flown on the FIREBIRD mission; and the Atmospheric X-ray Imaging Spectrometer (AXIS), an instrument being developed at CU Boulder that will take novel images and spectra of 50–300 keV X-ray photons. This work describes the AEPEX mission overview, the detailed design and operation of AXIS, and initial test and calibration results

    Self-reported depression symptoms in haemodialysis patients: Bi-factor structures of two common measures and their association with clinical factors

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    Copyright © 2018 Elsevier Inc. All rights reserved.Objective: To validate the factor structure of two common self-report depression tools in a large sample of haemodialysis (HD) patients and to examine their demographic and clinical correlates, including urine output, history of depression and transplantation. Methods: Factor structures of the Beck Depression Inventory (BDI-II) and Patient Health Questionnaire (PHQ-9) were evaluated using confirmatory factor analysis (CFA). Data was utilised from the screening phase (n = 709) of a placebo-controlled feasibility randomised control trial (RCT) of sertraline in HD patients with mild to moderate Major Depressive Disorder. Alternative factor models including bi-factor models for the BDI-II and PHQ-9 were evaluated. Coefficient omega and omega-hierarchical were calculated. Results: For both measures, bi-factor measurement models had the overall best fit to the data, with dominant general depression factors. Omega-hierarchical for the general BDI-II and PHQ-9 factors was 0.94 and 0.88 respectively. Both general factors had high reliability (coefficient omega = 0.97 and 0.94 respectively) and explained over 85% of the explained common variance within their respective models. BDI-II and PHQ-9 general depression factors were negatively associated with age and urine output and positively with a history of depression, antidepressant use within the last 3 months and a history of failed transplantation. In adjusted regression models, age, urine output and a history of depression remained significant. Conclusions: These data suggest that both the BDI-II and PHQ-9 are sufficiently unidimensional to warrant the use of a total score. Younger age, lower urine output and a history of depression appear consistent correlates of depression severity among HD patients.Peer reviewedFinal Accepted Versio

    Focal, remote-controlled, chronic chemical modulation of brain microstructures

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    Direct delivery of fluid to brain parenchyma is critical in both research and clinical settings. This is usually accomplished through acutely inserted cannulas. This technique, however, results in backflow and significant dispersion away from the infusion site, offering little spatial or temporal control in delivering fluid. We present an implantable, MRI-compatible, remotely controlled drug delivery system for minimally invasive interfacing with brain microstructures in freely moving animals. We show that infusions through acutely inserted needles target a region more than twofold larger than that of identical infusions through chronically implanted probes due to reflux and backflow. We characterize the dynamics of in vivo infusions using positron emission tomography techniques. Volumes as small as 167 nL of copper-64 and fludeoxyglucose labeled agents are quantified. We further demonstrate the importance of precise drug volume dosing to neural structures to elicit behavioral effects reliably. Selective modulation of the substantia nigra, a critical node in basal ganglia circuitry, via muscimol infusion induces behavioral changes in a volume-dependent manner, even when the total dose remains constant. Chronic device viability is confirmed up to 1-y implantation in rats. This technology could potentially enable precise investigation of neurological disease pathology in preclinical models, and more efficacious treatment in human patients. Keywords: brain; drug delivery; substantia nigra; neural implant; PETNational Institutes of Health (U.S.) (Grant R01 EB016101)National Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant R01 EB016101)National Cancer Institute (U.S.) (Grant P30-CA14051

    Insects as Indicators of Habitat Quality, Ecological Integrity and Restoration Success in Illinois Prairies, Savannas and Woodlands

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    The typical methods that ecologists use for assessing habitat quality involves calculating quality based on primarily floristic data. This is true of evaluation of habitats in Illinois – although new methods have become available for assessing habitats based on other taxa. These alternative methods are often not in widespread use, especially in Illinois, and consist of using invertebrate indicator taxa to assess the ecological integrity of prairies, savannas, and woodlands (aquatic invertebrate survey tend to be more commonly used). There is a large diversity of invertebrates for which we have information on the life history, seasonality, and diet that live in these unique habitats. Critically, these organisms are often sensitive to environmental change and habitat fragmentation. Insects in particular can thus be valuable indicators of habitat quality and ecosystem integrity. For this study, we chose to look at four groups of insects as indicators, based on their life history, ease of identification, and knowledge of the co-authors. These groups are well represented in grassland biomes and include: (1) grasshoppers (Orthoptera: Acridoidea); (2) butterflies (Lepidoptera: Rhopalocera); (3) cicadas (Hemiptera: Cicadoidea); and (4) tiger beetles (Coleoptera: Carabidae). By looking at both the abundance and species diversity at a given site for each of these groups, we hoped to develop tools that would allow land managers to utilize these taxa as indicators of high quality prairie. This is not an entirely novel pursuit, grasshoppers and butterflies have consistently been shown to represent other invertebrate and plant taxa effectively in grasslands worldwide. Through this study we have developed a butterfly quality index tool for assessing sites. The taxa examined by our group also often rely on habitat quality that cannot be assessed by floristic data alone, for this we have gathered data on habitat heterogeneity.Illinois Department of Natural Resources, State Wildlife Grant Project Number T-92-R-1unpublishednot peer reviewedOpe

    The beginning of time? Evidence for catastrophic drought in Baringo in the early nineteenth century

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    New developments in the collection of palaeo-data over the past two decades have transformed our understanding of climate and environmental history in eastern Africa. This article utilises instrumental and proxy evidence of historical lake-level fluctuations from Baringo and Bogoria, along with other Rift Valley lakes, to document the timing and magnitude of hydroclimate variability at decadal to century time scales since 1750. These data allow us to construct a record of past climate variation not only for the Baringo basin proper, but also across a sizable portion of central and northern Kenya. This record is then set alongside historical evidence, from oral histories gathered amongst the peoples of northern Kenya and the Rift Valley and from contemporary observations recorded by travellers through the region, to offer a reinterpretation of human activity and its relationship to environmental history in the nineteenth century. The results reveal strong evidence of a catastrophic drought in the early nineteenth century, the effects of which radically alters our historical understanding of the character of settlement, mobility and identity within the Baringo–Bogoria basin

    Advanced LIGO Laser Systems for O3 and Future Observation Runs

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    The advanced LIGO gravitational wave detectors need high power laser sources with excellent beam quality and low-noise behavior. We present a pre-stabilized laser system with 70 W of output power that was used in the third observing run of the advanced LIGO detectors. Furthermore, the prototype of a 140 W pre-stabilized laser system for future use in the LIGO observatories is described and characterized
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